Mud-puddling

Another long, hot day of fieldwork. This summer has been such a contrast to the last one - I even have a reasonable tan! It's good to see that populations of many species of butterfly have recovered from the abysmal weather of 2012. I don't think I've ever seen more butterflies than I have over the last few days - both in long-established nature reserves and brownfield sites - clouds of whites, small tortoiseshells, peacocks, meadow browns, gatekeeper, marbled whites, ringlets and brown argus. The only species that still seems somewhat scarcer than normal is the common blue, though this may just be a bit late emerging.

The heavy rain of Monday night had left a number of puddles at our site, and for the first time I saw congregations of green-veined and small whites mud-puddling. This phenomenon is widely observed in the tropics but I've usually only seen singletons sipping from puddles or dung in the UK.

Butterflies get most of their nutrition from flower nectar. Though rich in sugar, nectar lacks some important nutrients the butterflies need for reproduction. For those, butterflies visit puddles. By sipping moisture from mud puddles, butterflies take in salts and minerals from the soil. This behavior is called puddling, and is mostly seen in male butterflies because males incorporate those extra salts and minerals into their sperm.

When butterflies mate, the nutrients are transferred to the female through the sperm. These extra salts and minerals improve the viability of the female's eggs, increasing the couple's chances of passing on their genes to another generation.

The largest group I saw was eight, and this image was taken as a new male came in to join the group. The arrival of a stranger stimulated a frenzy of wing flicking and flashing, before they all settled down peacefully again. I hope this bodes well for the next generation - though gardeners might not be so enthusiastic to see numbers soar!

We finished work about 4.30pm, when the temperature had reached 27.5C. We arrived home to find preparations for a celebration barbecue in full swing. I was given in ice-cold Mojito, which I sipped lying on the bed in my underwear. Decadent? I think so - but very well deserved after the last couple of weeks.